[Asterisk-Users] Setup suggestions/ideas

[jamesm]

    I am trying to figure out a safe way to do 911 service. I would like 
to have all my SIP phones register with a remote
Asterisk server and use it for inbound/outbound calls.  However when 
that server is no longer available or someone dials
911, i would like the SIP phones to fail over/use a local Asterisk 
server which will use the PSTN to call out.  Does anyone have
any ideas on how to make this work. Perhaps this can be accomplished by 
using a SIP proxy such as SER?